Reciprocating pump and use of said reciprocating pump

ABSTRACT

The invention relates to a reciprocating pump comprising a drive shaft ( 2 ) that is mounted in a housing ( 1 ) and that has a freely definable and in exceptional cases sinusoidal control curve ( 5 ). A transmission element ( 6 ) that is connected to a piston ( 4 ) penetrates the control curve ( 5 ). The transmission element ( 6 ) is guided in an elongated guide section ( 7 ) of the housing ( 1 ). The displacement directions of the piston ( 4 ) run parallel to the rotational axis of the drive shaft ( 2 ). The reciprocating pump is extremely compact and is particularly suitable for use as a fuel pump in a motor vehicle.

BACKGROUND OF THE INVENTION

The invention relates to a reciprocating pump with at least one piston arranged axially displaceably in a casing, with a rotatably mounted drive shaft for driving the piston, with an inlet channel and with an outlet channel. The invention relates, furthermore, to an advantageous use of the reciprocating pump.

The reciprocating pumps known from practice mostly have as drive shaft a crankshaft connected to the piston via a connecting rod. The inlet channel and the outlet channel each have valves. The valves may be positively controlled via a camshaft or have a spring element and be controlled via the pressure generated in the casing by the piston. A very high feed volume at a high feed pressure can be generated by means of an intended diameter and stroke travel of the piston and rotational speed of the drive shaft. The known reciprocating pump has the disadvantage that it has a very large construction space and a highly complicated construction.

To simplify the construction of the reciprocating pump, it is known, for example from DE 0 855 488, to drive the piston via a compensating drive. The pressure feed is achieved by means of the actual movement of the piston. A regulating control pressure piston executes a combined rotational and reciprocating movement and has a control groove on its outer surface area. This reciprocating pump has the disadvantage that it is of likewise highly complicated construction and is suitable only for low feed quantities.

The problem on which the invention is based is to design a reciprocating pump of the type initially mentioned in such a way that it is constructed in a particularly simple and compact way and makes it possible to have high feed capacity at a high feed pressure. Furthermore, advantageous use of the reciprocating pump is to be provided.

BRIEF DESCRIPTION OF THE INVENTION

The first mentioned problem is achieved, according to the invention, in that the drive shaft has a control curve with at least one upper reversal point and one lower reversal point, in that the piston is guided in the control curve, and in that a transmission element extends from the piston through an elongated guide in the casing into the control curve.

As a result of this configuration, the direction of movement of the piston can be arranged parallel to the drive shaft, thus allowing a particularly compact construction of the reciprocating pump. In the simplest instance, the control curve is configured sinusoidally over the circumference of the shaft and has in each case an upper and a lower reversal point. In the event of a rotation of the drive shaft over 180°, the piston is consequently moved in one direction, and, in the event of rotation over the next 180°, the piston is moved in the opposite direction. By virtue of this configuration of the control curve, the piston is driven in the same way as the piston connected to the crankshaft via the connecting rod. The feed pump according to the invention therefore has a high feed volume at a high feed pressure. A connecting rod mounted on the piston and mounted on the drive shaft is avoided by virtue of the invention. The reciprocating pump according to the invention therefore requires particularly few components to be mounted and consequently has a very simple construction. Preferably, the direction of movement of the piston is arranged parallel to the axis of rotation of the drive shaft. The piston of the reciprocating pump according to the invention may be sealed off with respect to the casing, for example, via sealing rings or via a diaphragm.

According to an advantageous development of the invention, a rotation of the transmission element can be prevented in a simple way if the transmission element is led through an elongated guide in the casing.

The reciprocating pump according to the invention requires only a single control curve for a plurality of pistons if a plurality of pistons are arranged concentrically with respect to the drive shaft.

The inlet channel could be arranged, for example, in the casing and have a control valve or be controlled by the movement of the piston. However, according to an advantageous development of the invention, the reciprocating pump according to the invention has a particularly compact configuration when the inlet channel passes through the piston and has a nonreturn valve. The outlet channel preferably has a nonreturn valve in the casing in the same way as known reciprocating pumps.

The reciprocating pump according to the invention has a particularly low axial construction height if the nonreturn valve of the inlet channel and/or a nonreturn valve of the outlet channel are/is designed as a diaphragm valve.

A contribution is made to a reduction in the radial dimensions of the reciprocating pump according to the invention when the nonreturn valve of the inlet channel and/or the nonreturn valve of the outlet channel have/has a valve body guided longitudinally displaceably and located opposite a valve seat. To assist the movements, the valve body may be prestressed relative to the valve seat by a spring element. In an instance which is particularly simple in structural terms, the valve bodies can be controlled, even without spring force, by the pressure in the casing.

According to another advantageous development of the invention, the manufacture of the piston requires a particularly low outlay if a recess provided in the piston for receiving the transmission element has a peripheral groove. The peripheral groove may in this case, for example, be of rectangular or trapezoidal design or have a segment of a circle.

The piston could, for example, be manufactured in one piece with a transmission element. However, according to another advantageous development of the invention, the piston can be manufactured particularly simply, without radially projecting components, when the piston has a pocket, shaped correspondingly to the transmission element, for receiving a part region of the transmission element. By virtue of this configuration, the piston is secured against rotation, and the connection between transmission element and piston can be mounted, for example, hydrostatically. A further advantage of this configuration is that, by means of the pocket, a surface support of the transmission element can be achieved, in contrast to the recess being designed as a peripheral groove. The reciprocating pump according to the invention consequently has particularly low wear. The pocket may be designed, for example, as a cylindrical bore or a conical bore or have a form of a spherical cap corresponding to the transmission element. Furthermore, the transmission element can be pressed into the pocket, and consequently a relative movement of the piston with respect to the transmission element can be avoided. This leads to a further reduction in the wear of the reciprocating pump according to the invention.

The reciprocating pump according to the invention can be composed of particularly cost-effective components if the transmission element is designed as a ball. Preferably, in this case, the control curve of a cross section is designed as a partial circle.

According to another advantageous development of the invention, a rotation of the transmission element can be reliably avoided if the transmission element is designed as a rotationally symmetrical sliding block. The control curve preferably has in this case a rectangular or trapezoidal cross section.

The reciprocating pump according to the invention has a particularly simple structural configuration when the guide in the casing is arranged on a straight line connecting the axes of symmetry of the piston and of the drive shaft.

According to another advantageous development of the invention, the transmission element can be provided with particularly large dimensions, without this contributing to increasing the radial dimensions of the reciprocating pump according to the invention, if the guide in the casing is arranged outside the straight line connecting the axes of symmetry of the piston and of the drive shaft.

According to another advantageous development of the invention, a play of the transmission element in the guide of the casing or in the control curve can be compensated in a simple way if lateral bearing faces of the guide of the transmission element in the casing and/or of the control curve are prestressed relative to one another. As a result, the transmission element is guided particularly accurately, and therefore wear is kept particularly low.

According to another advantageous development of the invention, the control curve can have a particularly long configuration if the drive shaft has, in the region of the piston, a rim surrounding the piston at least partially radially on the outside and the control curve is arranged on the rim radially on the inside. The drive shaft consequently surrounds the piston.

The control curve, of particularly long configuration, is subject to particularly low wear.

The contribution to a further reduction in the wear of the control curve is made when the piston is arranged between two control curves one radially surrounding the other concentrically.

According to another advantageous development of the invention, the drive shaft can be operated at a particularly low rotational speed if the control curve has a plurality of upper and lower reversal points over the circumference of the drive shaft.

The intake and ejection of the medium to be fed require, as a rule, a different energy consumption. According to another advantageous development of the invention, different torques on the drive shaft can be avoided in a simple way if the control curve has during an intake stroke at least one curve function other than during an ejection stroke. This contributes to a reduction in vibrations of the reciprocating pump according to the invention. The control curve and consequently the intended sequence of movement of the piston over the angle of rotation of the drive shaft are freely definable by virtue of the invention.

The control curve may be composed of even a plurality of curve functions. The piston can therefore move according to the equations x=(m+r) and m=360°−r, x being a number of strokes per drive shaft revolution, m being the angular range of the drive shaft during the upward movement of the piston, and r being the angular range of the drive shaft during a downward movement of the piston. At x=1, m=240° and r=120°, the piston is moved upward to the upper reversal point in the event of a rotation of the drive shaft through 240° and is moved downward to the lower reversal point during the subsequent rotation of the drive shaft through 120°.

The second-mentioned problem, to be precise the determination of an advantageous use of the reciprocating pump, is solved, according to the invention, by use as a fuel pump in a structural unit with a motor for driving the drive shaft.

In fuel pumps of present-day motor vehicles, there is the problem, even when the fuel is hot, of generating a high feed pressure and a high feed volume. In motor vehicles with particularly high-power internal combustion engines, therefore, two feed units with fuel pumps designed, for example, as side channel pumps or as gerotor pumps are often employed.

These feed units therefore also require two electric motors for driving the fuel pumps. By virtue of the invention, a plurality of pistons can be operated simultaneously by a single drive shaft, thus leading to a particularly simple construction of the feed unit.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention permits numerous embodiments. To make it even clearer, several of these are illustrated in the drawing and are described below. In the drawing:

FIG. 1 shows a longitudinal section through a reciprocating pump according to the invention.

FIG. 2 shows a sectional illustration through the reciprocating pump from FIG. 1 along the line II-II.

FIG. 3 shows a sectional illustration through a further embodiment of the reciprocating pump according to the invention.

FIG. 4 shows diagrammatically a longitudinal section through a further embodiment of the reciprocating pump according to the invention.

FIG. 5 shows diagrammatically a longitudinal section through a further embodiment of the reciprocating pump according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a longitudinal section through a fuel pump with a drive shaft 2 mounted in a casing 1. The casing 1 has a cylindrical bore 3 with a piston 4 guided axially movably therein. The drive shaft 2 has a control curve 5 for receiving a part region of a transmission element 6. The transmission element 6 passes through an elongated guide 7 arranged parallel to the axis of rotation of the drive shaft 2, located in the casing 1 and projecting into a recess 8 of the piston 4, said recess being designed as a peripheral groove. An inlet channel 9 passes through the piston 4. An outlet channel 10 is arranged in the casing 1.

Valves 11, 12 designed as nonreturn valves and having valve bodies 17, 18 prestressed relative to valve seats 15, 16 by spring elements 13, 14 are arranged in each case in the inlet channel 9 and the outlet channel 10.

The control curve 5 has an upper reversal point 19 and a lower reversal point 20. The piston 4 is illustrated in the drawing at the upper reversal point 19. In the event of a rotation of the drive shaft 2, the transmission element 6 slides to the control curve 5 and into the guide 7 of the casing 1 and at the same time displaces the piston 4 away from the outlet channel 10. In this case, the valve 12 in the outlet channel 10 closes. This gives rise to a vacuum in the space delimited by the piston 4 and the casing 1, with the result that the valve 11 in the inlet channel 9 opens and a medium to be fed is sucked in. The valve 11 in the inlet channel 9 closes at the lower reversal point 20. When the drive shaft 2 is rotated further beyond the lower reversal point 20, this gives rise, in the space delimited by the piston 4 and the casing 1, to a pressure which presses the valve body 18 of the valve 12 in the outlet channel 10 away from the valve seat 16. The medium to be fed is consequently ejected through the outlet channel 10.

FIG. 2 shows, in a sectional illustration through the reciprocating pump from FIG. 1 along the line II-II, that overall three pistons 4, 4′, 4″ are arranged in the casing 1 concentrically around the drive shaft 2. The casing 1 is consequently designed as a cylinder support and guides a plurality of pistons 4, 4′, 4″. Of course, even more than three pistons 4, 4′, 4″ may be arranged in the casing 1. Each of the pistons 4, 4′, 4″ is connected to the single control curve 5 of the drive shaft 2 via a transmission element 6, 6′, 6″. The guides 7, 7′, 7″ for the transmission elements 6, 6′, 6″ are designed as bores. Axes of symmetry of the drive shaft 2, of the piston 4, 4′, 4″and of the guides 7, 7′, 7″ are arranged in each case on a straight line.

FIG. 3 shows a further embodiment of the reciprocating pump in a sectional illustration, which differs from that of FIG. 2, above all, in that the axes of symmetry of the guides 7, 7′, 7″ are arranged outside straight lines running from the axes of symmetry of the driving shaft 2 and the pistons 4, 4′, 4″. Furthermore, bearing faces 21 of the guides 7, 7′, 7″, said bearing faces bearing against the transmission elements 6, 6′, 6″, are arranged on tension elements 23 prestressed by spring elements 22. The transmission elements 6, 6′, 6″ are consequently prestressed in the guides 7, 7′, 7″.

FIG. 4 shows diagrammatically a longitudinal section through a further embodiment of the reciprocating pump, in which a drive shaft 24 has a rim 26 surrounding a piston 25 radially on the outside. A control curve 27 is arranged on the radial inner side. A casing 28 arranged radially within the rim 26 has a cylindrical bore 29 for guiding a piston 25. A 20 transmission element 30 is pressed in a recess 31, designed as a pocket, of the piston 35 and passes through the casing 28 in the region of a guide 32 running parallel to the axis of rotation of the drive shaft 24 and penetrates into the control curve 27. The control curve 27 has a rectangular cross section. As in the embodiment according to FIGS. 1 and 2, here too a plurality of pistons 25 may be arranged concentrically about the axis of rotation of the drive shaft 24. An inlet channel 33 and an outlet channel 34 are arranged, in each case with valves 35, 36 designed as nonreturn valves, in the casing 28.

FIG. 5 shows a further embodiment of the reciprocating pump, in which a drive shaft 37 has a shaft stub 38 with a first control curve 40 and a rim 39 concentrically surrounding the shaft stub 38 and having a second control curve 41.

Between the shaft stub 38 and the rim 39, a piston 42 is guided axially displaceably in a bore 43 of a casing 44. Transmission elements 45, 46 guided in the control curves 40, 41 pass in each case through elongated guides 47, 48 in the casing 44 and project into a recess 49, 50 of the piston 42, said recess being designed as a pocket. In the casing 44, an inlet channel 51 and an outlet channel 52 with valves 53, 54 designed as diaphragm valves are arranged.

The valves 53, 54 have a resiliently elastic diaphragm 57, 58 prestressed towards valve seats 55, 56. The control curves 40, 41 in each case have a trapezoidal cross section. A bearing face of the radially outer control curve 41 is arranged on a tension element 60. The tension element 60 is screwed to the casing 44 and is prestressed against the latter by cup springs 61. Similarly, of course, the control curve 40 of the shaft stub 38 may also be provided with a prestressed bearing face or the shaft stub 38 is prestressed axially with respect to the radially outer control curve 41. 

1. A reciprocating pump with at least one piston arranged axially displaceably in a casing, with a rotatably mounted drive shaft for driving the piston, with an inlet channel and with an outlet channel, characterized in that the drive shaft has a control curve with at least one upper reversal point and one lower reversal point, in that the piston is guided in the control curve, and in that a transmission element extends from the piston into the control curve.
 2. The reciprocating pump as claimed in claim 1, characterized in that the transmission element is led through an elongated guide in the casing.
 3. The reciprocating pump as claimed in claim 1 or 2, characterized in that a plurality of pistons are arranged concentrically with respect to the drive shaft.
 4. The reciprocating pump as defined in claim 1, wherein the inlet channel passes through the piston and has a nonreturn valve.
 5. The reciprocating pump as defined in claim 4, wherein the nonreturn valve of the inlet channel and/or a nonreturn valve of the outlet channel are/is designed as a diaphragm valve.
 6. The reciprocating pump as defined in claim 4, wherein the nonreturn valve of the inlet channel and/or the nonreturn valve of the outlet channel have/has a valve body guided longitudinally displaceably and located opposite a valve seat.
 7. The reciprocating pump as defined in claim 1, wherein a recess in the form of a peripheral groove is provided for receiving the transmission element.
 8. The reciprocating pump as defined in claim 1, wherein the piston has a pocket, shaped correspondingly to the transmission element, for receiving a part region of the transmission element.
 9. The reciprocating pump as defined in claim 8, wherein the transmission element is designed as a ball.
 10. The reciprocating pump as defined in claim 8, wherein the transmission element is designed as a sliding block.
 11. The reciprocating pump as defined in claim 2, wherein the guide in the casing is arranged on a straight line connecting the axes of symmetry of the piston and of the drive shaft.
 12. The reciprocating pump as defined in claim 2, wherein the guide in the casing is arranged outside the straight line connecting the axes of symmetry of the piston and of the drive shaft.
 13. The reciprocating pump as defined in claim 2, wherein the guide of the transmission element has lateral bearing faces that are prestressed relative to one another.
 14. The reciprocating pump as defined in claim 1, wherein the drive shaft has a rim surrounding the piston at least partially radially on the outside, and the control curve is arranged on the rim radially on the inside.
 15. The reciprocating pump as defined in claim 1, wherein the piston is arranged between two control curves, in which one radially surrounds the other concentrically.
 16. The reciprocating pump as defined in claim 1, wherein the control curve has a plurality of upper and lower reversal points over the circumference of the drive shaft.
 17. The reciprocating pump as defined in claim 1, wherein the control curve has, during an intake stroke, at least one curve function other than during an ejection stroke. 